netOrk drove this driver's shell through the private `_send` (an
interactive PTY, stdout and stderr merged, no exit code) and opened its
own paramiko connections for Docker. napalm-device-types 2.6.0 makes the
channel public; this implements it (NetOrk/netork#765):
- `run_command()` and `open_stream()` open an exec channel on the SSH
transport netmiko already holds: no second login, no PTY, a real exit
status.
- `privileged=True` follows the driver's existing rules: as root the
command runs directly; with a sudo password it goes through
`sudo -S -p ''` and the password is written to stdin, never onto the
command line; without one `sudo -n` fails at once instead of hanging.
- `ContainerEngineMixin` is mixed in, so `open_container_engine("docker")`
streams the Engine API over `docker system dial-stdio`.
The existing Docker methods are unchanged. Version 0.2.0, requires
napalm-device-types >= 2.6.0.
Refs NAPALM/napalm-device-types#17
